Surgical forceps capable of adjusting sealing pressure based on vessel size

ABSTRACT

A surgical forceps includes a housing having one or more shafts attached thereto and an end effector assembly disposed at a distal end thereof. The end effector assembly includes first and second jaw members disposed in opposing relation relative to one another. At least one jaw member is moveable from an open position to a closed position for grasping tissue therebetween. The jaw members include at least one sensing component that determines an output of one or both of cross-sectional diameter and composition of tissue disposed between the jaw members. A processing component is configured to receive the output and determine a seal pressure for adequately sealing tissue disposed between the jaw members based upon the output. A regulating component regulates the movement of the jaw members between the first and second positions such that the determined seal pressure is applied to tissue disposed therebetween.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patent application Ser. No. 12/619,100, filed on Nov. 16, 2009, the entire contents of which are hereby incorporated herein by reference.

BACKGROUND

Technical Field

The present disclosure relates to a surgical forceps, and more particularly, to a surgical forceps and method for determining and applying a minimum seal pressure to tissue based upon tissue diameter and/or composition.

Background of Related Art

As an alternative to open forceps for use with open surgical procedures, modern surgeons use endoscopic or laparoscopic instruments for remotely accessing organs through smaller, puncture-like incisions. More recently, Natural Orifice Translumenal Endoscopic Surgery (NOTES) procedures have been developed, for example, to access the abdominal cavity via the mouth, for scar-less surgery. Much like laparoscopy, NOTES is beneficial to patients in that it reduces healing time. However, while these minimally invasive surgical procedures are advantageous in many respects, the reduced access area presents new problems for surgical instrument design. For example, achieving a high seal pressure with a surgical forceps becomes increasingly more difficult as the size of the jaw members decreases. Accordingly, determining a minimum seal pressure needed to effectively seal tissue having a given diameter would be helpful in designing surgical instrument for use in laparoscopic or NOTES procedures.

Further, the proper seal pressures, or seal pressure ranges, required to effectively seal vessels of particular diameters is also important. Accurate application of pressure is important to oppose the walls of the vessel, to reduce the tissue impedance to a low enough value that allows enough electrosurgical energy through the tissue, to overcome the forces of expansion during tissue heating, and to contribute to the end tissue thickness which is an indication of a good seal. If the pressure is not great enough, the vessel may not properly or effectively seal and if the pressure is too great, the seal may shred or tear. It has been found that the amount of force required to produce an effective seal is at least partly dependent on the size and composition of the tissue to be sealed. Therefore, in order to help ensure an adequate seal, it would be advantageous to initially determine the size and/or composition of the tissue to be sealed and then apply the appropriate seal pressure.

Accordingly, a study was conducted to determine how seal pressure and blood vessel size influence the quality of the seal produced, measured through burst pressure. Seal pressure refers to the force imparted to tissue disposed, for example, between opposing jaw members of a surgical forceps. Burst pressure is the pressure required to open, or burst, a previously sealed vessel by forcing a fluid through the sealed vessel. The study was designed using a central composite response surface, a well known Design of Experiments (DoE) variation. The DoE contained two factors: seal pressure and vessel size. The range of values tested for seal pressure was 40 psi to 120 psi, while the vessel diameters ranged from 2 mm to 6 mm.

In testing, porcine renal arteries were removed and dissected and the diameter of the vessel was measured. The vessel was then placed on a research tool used for electrothermal bipolar vessel sealing. The pressure between the jaw members was set on the research tool to correspond with the appropriate seal pressure dictated by the DoE. A vessel seal was produced by applying bipolar energy to the seal plates using a ForceTriad™ generator manufactured by Valleylab (now Covidien Energy-based Devices) of Boulder, Colo. Once the seal was made, the vessel was held in place while water was pumped through the vessel for burst testing. A pressure calibrator was used to determine the maximum pressure the vessel could withstand prior to bursting. The burst pressures for all of the vessel sizes and pressure combinations were input into a statistical software package for further analysis. An Analysis of Variation (ANOVA) evaluation revealed that both vessel size and seal pressure were significant factors in determining the burst pressure (quality) of the resultant seal.

SUMMARY

In accordance with the present disclosure, a surgical forceps is provided. The forceps includes a housing and one or more shafts attached to the housing. An end effector assembly is disposed at a distal end of the shaft(s). The end effector assembly includes first and second jaw members disposed in opposing relation relative to one another. One or both of the jaw members is moveable from an open position to a closed position for grasping tissue. The jaw members include one or more sensing components that determine an output of cross-sectional diameter and/or composition of tissue disposed between the jaw members. A processing component is configured to receive the output from the sensing components and determine a seal pressure for adequately sealing tissue based upon the output. A regulating component, in communication with the processing component, is configured to regulate the movement of the jaw members such that upon movement from the open to the closed position, the determined seal pressure is applied to tissue disposed between the jaw members.

In one embodiment, the sensing component includes a pair of electrodes disposed through each of the jaw members. The electrodes are configured to pass an electrical signal through tissue disposed between the jaw members. The electrodes can thereby measure one or more electrical characteristics of tissue and determine the cross-sectional diameter and/or the composition of tissue. In one embodiment, the electrodes are configured to measure the impedance through tissue.

In another embodiment, the processing component includes an electrical circuit configured to receive the output from the sensing component and determine a seal pressure corresponding to that output.

In yet another embodiment, a generator, in communication with the processing component is provided. The generator is configured to store user-input data and use that data to, in conjunction with the processing component, determine a seal pressure corresponding to the output from the sensing component.

In still yet another embodiment, the regulating component includes a mechanically-driven system, an electrically-driven system and/or an electro-mechanically-driven system to regulate the seal pressure between the jaw members.

In yet another embodiment, the seal pressure determined by the processing component is a minimum seal pressure required to adequately seal tissue according to the output.

In another embodiment, the seal pressure determined by the processing component is a range of seal pressures for adequately sealing tissue according to the output.

A method of sealing tissue is also provided in accordance with the present disclosure. The method includes providing a surgical forceps having first and second jaw members disposed in opposing relation relative to one another. One or both of the jaw members are moveable from an open position to a closed position for grasping tissue. The method also includes the steps of determining a cross-sectional diameter and/or a composition of tissue disposed between the jaw members, determining a seal pressure for adequately sealing tissue according to the cross-sectional diameter and/or composition, and regulating the movement of the jaw members. The movement of the jaw members is regulated such that upon movement from the open to the closed position, the seal pressure is applied to tissue disposed the jaw members.

In another embodiment, the determined seal pressure is a minimum seal pressure required to adequately seal tissue.

In yet another embodiment, the determined seal pressure is a range of seal pressures for adequately sealing tissue.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the subject instrument are described herein with reference to the drawings wherein:

FIG. 1 is a top, perspective view of a surgical forceps including a housing, a handle assembly, a shaft, and an end effector assembly, for use with the present disclosure;

FIG. 2 is a enlarged, side, perspective view of the end effector assembly of FIG. 1, wherein the top jaw is shown with parts separated;

FIG. 3 is a side, perspective view of the housing of the forceps of FIG. 1, with a half of the housing removed;

FIG. 4 is flow chart illustrating a method of sealing tissue in accordance with the present disclosure;

FIG. 5 is a contour plot of mean burst pressure as a result of seal pressure and vessel size with 0.083 inch wide seal plates; and

FIG. 6 is a contour plot of the mean burst pressure as a result of seal pressure and vessel size with 0.029 inch wide seal plates.

DETAILED DESCRIPTION

Turning now to FIG. 1, an endoscopic forceps 10 is shown that includes a housing 20, a handle assembly 30, a rotating assembly 80, a trigger assembly 70 and an end effector assembly 100. Forceps 10 further includes a shaft 12 having a distal end 14 configured to mechanically engage end effector assembly 100 and a proximal end 16 that mechanically engages housing 20. Forceps 10 also includes electrosurgical cable 310 that connects forceps 10 to a generator 300. Cable 310 has sufficient length to extend through shaft 12 in order to provide electrical energy to at least one of jaw members 110 and 120 of end effector assembly 100.

With continued reference to FIG. 1, rotating assembly 80 is integrally associated with housing 20 and is rotatable approximately 180 degrees in either direction about a longitudinal axis “A.” The housing 20 includes two halves that house the internal working components of the forceps 10. Handle assembly 30 includes a moveable handle 40 and a fixed handle 50. Fixed handle 50 is integrally associated with housing 20 and handle 40 is moveable relative to fixed handle 50 in the direction of arrow “B” (see FIG. 3).

Referring now to FIG. 2, end effector assembly 100 is configured for mechanical attachment at the distal end 14 of shaft 12 of forceps 10. End effector assembly 100 includes a pair of opposing jaw members 110 and 120. Handle 40 of forceps 10 (see FIG. 1) ultimately connects to a drive assembly (not shown) which, together, mechanically cooperate to impart movement of the jaw members 110 and 120 from a first, open position wherein the jaw members 110 and 120 are disposed in spaced relation relative to one another, to a second, clamping or closed position wherein the jaw members 110 and 120 cooperate to grasp tissue therebetween.

With continued reference to FIG. 2, opposing jaw members 110 and 120 are pivotably connected about pivot 103 via pivot pin 105. Jaw members 110 and 120 include electrically conductive sealing plates 112 and 122 that are dimensioned to securely engage tissue when clamped therebetween. Each of the jaw members 110 and 120 also include a sensing component, or electrode pair 114 and 124, respectively, disposed therethrough. The electrode pairs 114 and 124 cooperate to measure the impedance across tissue disposed between the jaw members 110 and 120. Electrode pair 114 of jaw member 110, for example, may be configured to transmit a low-voltage alternating-current through tissue disposed between the jaw members 110 and 120, while electrode pair 124 of jaw member 120 may be configured to receive the resulting voltage after it has passed through tissue. It is also envisioned that this configuration may be reversed, e.g., where the transmitting electrodes are disposed through jaw member 120 and where the receiving electrodes are disposed through jaw member 110. In either configuration, the impedance across the tissue can be measured and used to determine the cross-sectional diameter of the tissue. Alternatively, the impedance across the tissue measured by the pairs of electrodes 114 and 124 can be used to determine the resistivity of the tissue. Since different components of tissue, e.g., muscle cells, fat cells and fluid, have different resistivities, determining the overall resistivity of the tissue can help determine the relative composition of the tissue. Further, a second pair of electrodes (not shown) or sensors may be disposed through each of the jaw members 110 and 120 such that the first set of electrode pairs 114 and 124 may be configured to measure the cross-sectional diameter of the tissue while the second set of electrode pairs is configured to measure the resistivity of the tissue.

It is also envisioned that any other suitable impedance sensing component may be provided in cooperation with jaw members 110 and 120 to measure the cross-sectional diameter and/or to determine the composition of tissue disposed between jaw members 110 and 120. Further, it is envisioned that the sensing component could include sensors disposed along the sealing plates 112 and 122 of jaw members 110 and 120, respectively, for sensing the gap distance between the respective sealing plates 112 and 122. By determining the gap distance between the sealing plates 112 and 122 at different positions along the plates, the size of the vessel grasped therebetween can be estimated.

Ultimately, the sensing component may be configured to measure any electrical or physical characteristic of tissue that may be used to determine a diameter of tissue or tissue composition. Accordingly, any sensor that may be used to measure an electrical or physical characteristic of tissue may be provided for use with end effector assembly 100 of forceps 10. Suitable sensors include, but are not limited to, impedance sensors, proximity sensors, optical sensors, ultrasonic sensors, chemical sensors, and the like.

Referring now to FIG. 3, housing 20 of forceps 10 is shown having a half of housing 20 removed. A processing component 21, disposed within housing 20, is configured to receive an output, e.g., a cross-sectional diameter and/or a composition of tissue from the sensing component 114. One or more leads 33, 37 are disposed through the housing 20 and shaft 12 to the jaw members 110 and 120 to provide feedback to the processing component 21. The processing component 21 converts the output into a seal pressure according to specific the characteristics, e.g., the cross-sectional diameter and/or the composition, of the tissue to be sealed. It is envisioned that the processing component 21 may determine the minimum seal pressure required to adequately seal the tissue disposed between the jaw members 110 and 120. Alternatively, the processing component 21 may be configured to determine a seal pressure range for sealing tissue disposed between the jaw member 110 and 120.

The processing component 21 includes electrical circuitry 22 configured to convert the output into a seal pressure, or seal pressure range, for adequately sealing tissue disposed between the jaw members 110 and 120. Electrical circuitry 22 may be configured to convert the output to a seal pressure according to specific parameters and/or data. Alternatively, electrical circuitry 22 may communicate with an external source, e.g. generator 300, for determining the seal pressure corresponding to the tissue cross-sectional diameter and/or composition. Further, a computer chip (not shown) may be provided for storing data and communicating with the electrical circuitry 22 in order to determine the appropriate seal pressure, or seal pressure range, based upon the output from the sensing component 114. Specific data sets, e.g., the set of minimum seal pressures required for adequate sealing of vessels having varying cross-sectional diameters, may be used to convert the output cross-sectional diameter into a seal pressure. Algorithms can also be used to determine the seal pressure based upon the specific output. Exemplary data, determined by a study of seal pressure as a function of vessel size, for configuring the processing component 21, will be discussed in detail below.

With continued reference to FIG. 3, a regulating component 23 is shown in communication with the processing component 21 via lead 39. Regulating component 23 regulates movement of the jaw members 110 and 120 such that the determined seal pressure, or seal pressure range, is imparted to tissue disposed therebetween. Regulating component 23 may be an electro-mechanical component or a mechanical component, e.g., a system of gears 23, configured to define a specific range of motion of moveable handle 40 with respect to fixed handle 50. In such an embodiment, regulating component 23 would operate to limit the displacement of tabs 42 a and 42 b about pivot 43, thereby limiting the movement of moveable handle 40 with respect to fixed handle 50. Accordingly, a user would be prevented from squeezing handle 40 beyond a certain point. For example, if the determined seal pressure required to seal tissue disposed between jaw members 110 and 120 was relatively small, regulating component 23 would operate to prevent handle 40 from moving past position “C.” However, if the determined seal pressure were larger, regulating component 23 would operate to allow handle 40 to be moveable to position “D.” The movement of handle 40 to specific positions, e.g., position “C” or position “D,” corresponds to a specific seal pressure imparted to tissue, since handle 40 and drive assembly (not shown) cooperate to impart movement of the jaw members 110 and 120 from the open to the closed position. Therefore, defining a specific range of motion of handle 40 allows the determined seal pressure (corresponding to the fully squeezed position, e.g., position “C” or position “D”) to be applied to tissue disposed between jaw members 110 and 120. Accordingly, a user need not selectively squeeze handle 40 to approximate the proper seal pressure, but may squeeze handle 40 through its allowed range of motion (as defined by regulating component 23), thereby imparting the proper seal pressure to tissue disposed between jaw member 110 and 120.

As can be appreciated, the specific range of motion of handle 40 is determined by the seal pressure communicated to the regulating component 23 by the processing component 21. Alternatively, regulating component 23 may be electro-mechanically operated but may be configured to function in a similar manner. Further, any suitable regulating component capable of regulating movement of the jaw members 110 and 120 according to a determined seal pressure or seal pressure range, may be used in accordance with the present disclosure.

With reference now to FIG. 4, a method of sealing tissue is shown for use with forceps 10. First, a cross-sectional diameter and/or composition of tissue disposed through jaw members 110 and 120 of a forceps 10 is determined as an output. The output is then used to determine a seal pressure required for adequately sealing tissue according to pre-determined data and/or specifications. The determined seal pressure is then used to regulate the movement of the jaw members 110 and 120 such that the determined seal pressure is applied to tissue between jaw member 110 and 120 to thereby effectively seal tissue disposed therebetween.

As mentioned above, specific data may be input into the processing component 21 to determine the appropriate seal pressure corresponding to the specific tissue cross-sectional diameter and/or composition. In the study discussed above, vessels having diameters ranging from 2 mm to 6 mm were sealed by applying seal pressures ranging from 40 psi to 120 psi. Table 1, below, shows the results of the above-mentioned study, wherein the seal pressures indicated refer to the minimum seal pressure required to affect an adequate seal. The exemplary data represented in FIG. 1 corresponds to seal plate 112 and 122 (see FIG. 2) widths of 0.083 inches.

VESSEL DIAMETER (mm) MINIMUM SEAL PRESSURE (psi) 2 41 3 30 4 37 5 60 6 103

The minimum seal pressure was determined as the seal pressure required to produce a seal having a 98.5% probability of a burst pressure greater than 360 mmHg. However, depending on the vessel or tissue to be sealed, a greater (or smaller) burst pressure may be desired to ensure proper sealing. As such, the data would need to be altered accordingly. FIG. 5 shows the contour plot of the mean burst pressure as a result of seal pressure and vessel size with 0.083 inch wide seal plates 112 and 122. The points on the plot represent the probability of a burst pressure greater than 360 mmHg according to the specific vessel size and seal pressure tested.

As mentioned above, this data may be used in conjunction with processing component 21 of forceps 10 having seal plates 112 and 122 of 0.083 inch widths, to determine the proper seal pressure to apply to a vessel having a given cross-sectional diameter. For example, end effector assembly 100 of forceps 10 may be positioned such that a vessel is disposed between jaw members 110 and 120. The sensing component 114 may then determine that the cross-sectional diameter of the vessel is, for example, 6 mm. This output, e.g., a 6 mm cross-sectional diameter, would then be communicated to the processing component 21. If the processing component 21 was configured with the data from Table 1, above, the processing component 21 would determine that a minimum seal pressure of 120 psi would be required to effectively seal the 6 mm vessel disposed between the jaw members 110 and 120. Accordingly, the regulating component 23 would regulate the movement of the jaw members 110 and 120 such that when handle 40 is squeezed, thereby closing jaw members 110 and 120, a seal pressure of 120 psi is applied to seal the vessel disposed between jaw members 110 and 120. Thus, the user can be confident that the tissue seal created has approximately a 98.5% probability of a burst pressure greater than 360 mmHg. As can be appreciated, the input data can be adjusted to achieve a higher, or lower, seal quality probability.

Table 2, below, shows the results of the above-mentioned study, wherein the seal plate 112 and 122 widths are 0.029 inches.

VESSEL DIAMETER (mm) MINIMUM SEAL PRESSURE (psi) 2 <23 3 33 4 33 5 54 6 92 As with Table 1, the minimum seal pressures in Table 2 were determined as the seal pressure required to produce a seal having a 98.5% probability of a burst pressure greater than 360 mmHg. FIG. 6, corresponding to the data of Table 2, shows the contour plot of the mean burst pressure as a result of seal pressure and vessel size with 0.029 inch wide seal plates 112 and 122. As with the data from Table 1, this data may be used in conjunction with processing component 21 of forceps 10 having seal plates 112 and 122 of 0.029 inch widths, to determine the proper seal pressure to apply to a vessel having a given cross-sectional diameter.

As described above, the minimum seal pressures required to adequately seal vessels having a given diameter shown in Table 1 and Table 2, above, may be input into the processing component 21. Thus, in operation, as jaw member 110 and 120 of forceps 10 are moved to the closed position with tissue grasped therebetween, regulating component 23 ensures that the minimum seal pressure is applied to tissue, thereby helping to ensure an effective seal. Regulating component 23 also helps prevent tissue damage as a result of too much pressure being applied by preventing excess pressure from being applied to the tissue. Further, the contour plots of FIGS. 5 and 6 may be used to define a seal pressure range according to the vessel cross-sectional diameter determined by the sensing components 114 and 124.

Determining a minimum seal pressure is also useful in the design and manufacturing of forceps, such as forceps 10. Knowing the minimum amount of pressure needed to seal a vessel having a particular diameter provides a designer with a specific seal pressure the device must be able to achieve. For example, if a given forceps 10 is to be designed for use with vessels ranging from 2 mm to 6 mm, the designer must create a forceps having a seal pressure capable of reaching the minimum seal pressure required for a 6 mm vessel. However, the designer need not create a forceps capable of achieving a higher seal pressure. Knowing the actual force required for a given vessel size allows the designer to avoid unnecessary constraints while designing the forceps. This is especially useful when designing forceps for use in laparoscopic and/or NOTES procedures, since it is difficult to achieve high seal pressures with relatively small jaw members.

From the foregoing and with reference to the various figure drawings, those skilled in the art will appreciate that certain modifications can also be made to the present disclosure without departing from the scope of the same. While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto. 

What is claimed is:
 1. A forceps, comprising: an end effector assembly including first and second jaw members disposed in opposing relation relative to one another, at least one of the first and second jaw members movable relative to the other from a first position to a plurality of second positions, the first and second jaw members configured to grasp tissue therebetween in each of the plurality of second positions, at least one of the first and second jaw members including a sensor configured to sense at least one property of tissue disposed between the first and second jaw members and determine an output based upon the at least one sensed property; a handle assembly including a movable handle coupled to the end effector assembly, the movable handle movable between an initial position and a plurality of subsequent positions for moving the first and second jaw members between the first position and the plurality of second positions, respectively; a processor configured to receive the output from the sensor and determine a seal pressure for adequately sealing tissue disposed between the first and second jaw members based upon the output; and a regulator in communication with the processor and configured to receive the determined seal pressure from the processor, the regulator configured, based on the determined seal pressure received, to regulate a range of motion of the first and second jaw members between the first position and a selected one of the plurality of second positions such that movement of the first and second jaw members from the first position to the selected one of the plurality of second positions applies the determined seal pressure to tissue disposed between the first and second jaw members, the regulator disposed within the handle assembly and configured to regulate the range of motion of the first and second jaw members by limiting movement of the movable handle between the initial position and a selected one of the subsequent positions to thereby regulate the range of motion of the first and second jaw members.
 2. The forceps according to claim 1, wherein each of the first and second jaw members includes a sensor, the sensors of the first and second jaw members configured to pass an electrical signal through tissue disposed therebetween to measure an electrical characteristic therethrough, to thereby determine the at least one sensed property of tissue disposed therebetween.
 3. The forceps according to claim 2, wherein the electrical characteristic is impedance.
 4. The forceps according to claim 1, wherein the sensed property of tissue is cross-sectional diameter of tissue or composition of tissue.
 5. The forceps according to claim 1, wherein the regulator includes at least one of a mechanically-driven system, an electrically-driven system, or an electro-mechanically-driven system.
 6. The forceps according to claim 1, wherein the seal pressure determined by the processor is a minimum seal pressure required to adequately seal tissue according to the output.
 7. A forceps, comprising: an end effector assembly including first and second jaw members disposed in opposing relation relative to one another, at least one of the first and second jaw members movable relative to the other from a first position to a plurality of second positions, the first and second jaw members configured to grasp tissue therebetween in each of the plurality of second positions, each of the first and second jaw members including a sensor configured to sense at least one property of tissue disposed between the first and second jaw members and determine an output based upon the at least one sensed property, the sensors of the first and second jaw members configured to pass an electrical signal through tissue disposed therebetween to measure an electrical characteristic therethrough, to thereby determine the at least one sensed property of tissue disposed therebetween; a handle assembly including a movable handle coupled to the end effector assembly and configured to move the first and second jaw members between the first position and the plurality of second positions; a processor configured to receive the output from the sensor and determine a seal pressure for adequately sealing tissue disposed between the first and second jaw members based upon the output; and a regulator in communication with the processor and configured to receive the determined seal pressure from the processor, the regulator configured, based on the determined seal pressure received, to regulate a range of motion of the first and second jaw members between the first position and a selected one of the plurality of second positions such that movement of the first and second jaw members from the first position to the selected one of the plurality of second positions applies the determined seal pressure to tissue disposed between the first and second jaw members, the regulator disposed within the handle assembly and configured to regulate the range of motion of the first and second jaw members by limiting movement of the movable handle.
 8. A forceps, comprising: an end effector assembly including first and second jaw members disposed in opposing relation relative to one another, at least one of the first and second jaw members movable relative to the other from a first position to a plurality of second positions, the first and second jaw members configured to grasp tissue therebetween in each of the plurality of second positions, at least one of the first and second jaw members including a sensor configured to sense at least one property of tissue disposed between the first and second jaw members and determine an output based upon the at least one sensed property, wherein the sensed property of tissue is cross-sectional diameter of tissue or composition of tissue; a handle assembly including a movable handle coupled to the end effector assembly and configured to move the first and second jaw members between the first position and the plurality of second positions; a processor configured to receive the output from the sensor and determine a seal pressure for adequately sealing tissue disposed between the first and second jaw members based upon the output; and a regulator in communication with the processor and configured to receive the determined seal pressure from the processor, the regulator configured, based on the determined seal pressure received, to regulate a range of motion of the first and second jaw members between the first position and a selected one of the plurality of second positions such that movement of the first and second jaw members from the first position to the selected one of the plurality of second positions applies the determined seal pressure to tissue disposed between the first and second jaw members, the regulator disposed within the handle assembly and configured to regulate the range of motion of the first and second jaw members by limiting movement of the movable handle. 